Australian vessel Ocean Shield searching for the missing Malaysia Airlines plane has reacquired signals that could be consistent with “black box” flight recorders.

The Ocean Shield heard the signals again on Tuesday afternoon and evening, the search chief said.

Signals heard earlier had also been further analyzed by experts who concluded they were from “specific electronic equipment”, Angus Houston said.

Flight MH370 disappeared on March 8, carrying 239 people.

It was travelling from Kuala Lumpur to Beijing when it lost contact with air traffic controllers.

Malaysian officials say that based on satellite data, they believe it ended its flight in the southern Indian Ocean, thousands of miles from its intended flight path.

“I believe we are searching in the right area,” said Air Chief Marshal Angus Houston, who heads the joint agency co-ordinating the search.

Australian vessel Ocean Shield searching for the missing Malaysia Airlines plane has reacquired signals that could be consistent with “black box” flight recorders

“But we need to visually identify aircraft wreckage before we can confirm with certainty that this is the final resting place of MH370.”

The Ocean Shield has been towing a US Navy pinger locator to listen for signals from the plane’s flight recorders in waters west of the Australian city of Perth.

It twice acquired signals over the weekend.

On Tuesday, it located the signals again, the first time for five minutes and 32 seconds, and the second time for around seven minutes, said ACM Angus Houston.

“Ocean Shield has now detected four transmissions in the same broad area,” he said.

“Yesterday’s signals will assist in better defining a reduced and much more manageable search area on the ocean floor.”

The signals have been heard in sea with a depth of 15,000 feet.

ACM Angus Houston said it was important to refine the search area as much as possible before sending down the Bluefin 21 underwater drone to search for wreckage.

“Now hopefully with lots of transmissions we’ll have a tight, small area and hopefully in a matter of days we will be able to find something on the bottom,” he said.

Experts at the Australian Joint Acoustic Analysis Centre had also analyzed the first two signals heard over the weekend, he added.

Their analysis showed that a “stable, distinct and clear signal” was detected. Experts had therefore assessed that it was not of natural origin and was likely from specific electronic equipment.

“They believe the signals to be consistent with the specification and description of a flight data recorder,” ACM Angus Houston said.

Search teams have been racing against time to locate signals from the flight recorders before their batteries expire after about one month.

Investigators still do not know why MH370 strayed so far off course, after disappearing over the South China Sea between Malaysia and Vietnam.

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Australian defense vessel Ocean Shield searching for the missing Malaysia Airlines plane has detected signals consistent with those from black box flight recorders.

The Ocean Shield acquired the signal twice, once for more than two hours, said Air Chief Marshal Angus Houston, who is leading the search.

He called it the “most promising lead” so far.

However, ACM Angus Houston said more information was needed: “We haven’t found the aircraft yet and we need further confirmation.”

Malaysia Airlines plane, carrying 239 people, was flying from Kuala Lumpur to Beijing on March 8 when it disappeared. Malaysian officials say they believe it crashed in the southern Indian Ocean.

ACM Angus Houston said the signals were detected using the towed pinger locator deployed on the Ocean Shield.

Two separate detections occurred, he said. The first was held for two hours and 20 minutes before being lost.

The ship then turned around and on the return leg detected the signal again for 13 minutes.

Australian defense vessel Ocean Shield searching for the missing Malaysia Airlines plane has detected signals consistent with those from black box flight recorders (photo AP)

“On this occasion two distinct pinger returns were audible. Significantly this would be consistent with transmissions from both the flight data recorder and the cockpit voice recorder,” ACM Angus Houston said

“We are now in a very well defined search area, which hopefully will eventually yield the information that we need to say that [Malaysia Airlines flight] MH370 might have entered the water just here.”

The Ocean Shield was still in the area but had not been able to reacquire the signals since, he said.

The position of the signals needed to be fixed, ACM Angus Houston said. Once that happened, the Ocean Shield could lower the Bluefin 21 underwater autonomous vehicle to try to locate wreckage on the sea floor.

The signal had been heard in sea with a depth of 4,500m, he added, which was at the limit of the capability of the Bluefin 21.

ACM Angus Houston cautioned that the next steps would take time.

“It could take some days before the information is available to establish whether these detections can be confirmed as being from MH370,” he said.

“In very deep oceanic water, nothing happens fast.”

The search operation is in a race against time as the flight recorders’ batteries are due to run out, meaning a signal would no longer be emitted.

A Chinese search vessel, Haixun 01, also said it briefly heard signals over the weekend in a different search area.

Those signals are now being investigated with the help of a British naval vessel, HMS Echo, which is equipped with sophisticated sound-locating equipment.

Reports said the crew of the Chinese ship had been using a sonar device called a hydrophone to pick up sounds.

Experts said it was technically possible but unlikely that the sounds heard with this equipment related to the missing plane.

Chris Portale, a director of the US company Dukane which makes the device that emits signals from flight recorders, said looking for the Malaysian plane’s “black boxes” was like “looking for a suitcase on the side of a mountain” but under water.

So far, not a single piece of wreckage has been found from the missing plane, but officials have concluded – based on satellite data – that it ended its flight in the sea to the west of the Australian city of Perth.

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